Preparation Of Cobalt@Heteroatoms Doped Carbon Based Composite Materials And Their Electrocatalytic Performance For Oxygen Reduction Reaction

In the big setting of insufficient energy and severe environmental contamination,clean and sustainable energy have been the hot spot to research.Fuel cells(FCs)act as a kind of direct conversion equipment.So it possesses the high energy transformation efficiency,green and environmental conservation.The oxygen reduction reactions(ORR)in the cathode of FCs is the rate-determining step,where the noble metals(such as platinum and their alloys)usually act as the catalysts.However,there are a lot of shortcomings for the noble metal catalysts,for example high cost,less storage,low permanent durability and methanol resistance,which has limited their application widely.It is still a great challenge about preparing non-noble metal electrocatalysts to substitute for noble metal electrocatalysts towards ORR in FCs,which possess great activity and long-term stability.So,it is significant to research the non-noble metal oxygen reduction reaction catalysts.In this paper,we chose the low-cost biomass glucose and aluminium-based organic framework compound(MOF)MIL-101-NH2(Al)as the raw materials to synthesize the required catalyst carbon support.Then the materials were introduced the heteroatom and transition metal cobalt(Co)through the post-synthetic modification.Finally,transitionmetal compound complex heteroatom-doped carbon-based electrocatalysts with regard to ORR were obtained after elevated temperature pyrolysis in Hi-purity nitrogen atmosphere and tested their ORR property.The physical characterizations of the prepared catalysts have been tested through different test measurements,SEM.TEM,XRD,XPS,BET and Raman.In addition,the electrocatalytic characteristric was performed through employing electrochemical instrument.The staple contents of this paper are summed up as listed below:1.The low-cost biomass glucose was chosen as the raw materials to prepare the homogenous glucose spheres by hydrothermal self-assembly synthesis method.Then glucose spheres could adsorb Co2+ on the surface of glucose spheres via the electrostatic adsorption.Thiourea could completely decompose into NH3 and H2 S at high temperature,which could serve as heteroatom doping sources.After the high-temperature heat treatment,composites of nitrogen and sulfur co-doped glucose carbon spheres loaded with Co O were obtained(Co O@NS-CSs).Studies have shown that Co O@NS-CSs)possessed outstanding electrocatalytic property in alkaline solution,which the onset potential and the half-wave potential were 0.946 V and 0.821 V(vs.RHE),respectively.Cmpared to the commercial Pt/C,Co O@NS-CSs showed higher long-termtial stability and methanol tolerance.2.MIL-101-NH2(Al)was chosen as the host precursor as well as template,then the second ligand salicylaldehyde was introduced to chelate and immobilize Co2+ after onestep post-synthetic modification on account of the presence of open N site without coordination in the ligand.Finally,a series of composite catalysts which nirtrogen doped porous carbon materials loaded with metal cobalt and cobalt oxide(Co@NPC-X)t(X is the pyrolysis temperature/ oC,t is the alkaline etching times/h)were synthesized by the one-step pyrolysis in the high-purity nitrogen gas.Experiments explored the influence of different pyrolysis temperatures(700,800,900 o C)and alkaline etching times(t = 0,8,12,16 h)on ORR electrocatalytic activity,respectively through microstructure characterization and electrochemical measurement.The consequence signified that pyrolysis temperatures of 900 oC and the alkaline etching times of 12 h were the optimal experiment condition.The catalyst in optimal experiment condition prepared(Co@NPC-900)12 exhibited high ORR performance.